TY - JOUR
T1 - Seasonal variations in the light-absorbing properties of water-soluble and insoluble organic aerosols in Seoul, Korea
AU - Kim, Hwajin
AU - Kim, Jin Young
AU - Jin, Hyoun Cher
AU - Lee, Ji Yi
AU - Lee, Se Pyo
N1 - Funding Information:
This study was funded by the Korea Institute of Science and Technology (KIST) and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2011-0028597 ).
Publisher Copyright:
© 2016 Elsevier Ltd.
PY - 2016/3/1
Y1 - 2016/3/1
N2 - The spectral properties of light-absorbing organic aerosol extractions were investigated using 24-h average fine particulate matter (PM2.5) measurements from October 2012 to September 2013 in Seoul, Korea. The light-absorption spectra of water and methanol extracts exhibited strong evidence of brown carbon with Absorption Angstrom Exponent (AAE; fitted between 300 and 700 nm) ranges of 5.84-9.17 and 4.08-5.75, with averages of 7.23 ± 1.58 and 5.05 ± 0.67, respectively. The light absorption of both extracts at 365 nm (Abs365), which is typically used as a proxy for brown carbon (BrC), displayed strong seasonal variations and was well correlated with both water-soluble organic carbon (WSOC; r = 0.81) and organic carbon (OC; r = 0.85), indicating that both primary and secondary organics were sources of BrC in this region. Normalizing the Abs365 of water and methanol extracts to the mass of WSOC and OC yielded average solution mass absorption efficiency (MAE365) of 0.28-1.18 and 0.44-1.45 m2 g-1 C, respectively. MAE365 in Korea were in the same range or slightly lower than those in China, however, despite the same ranges, the seasonal variations were different, suggesting that the sources of light absorbers could be different. Combining the AAE, Abs365, and MAE365 of both extracts and a detailed chemical speciation of filter extracts identified the compounds responsible for the temporal variations of BrC in Korea. During summer, secondary organic aerosol (SOA), photochemically generated from anthropogenic emissions, was the major source; however, during winter, long range transported organics or transported BrC seem to be a source of BrC in Korea, a downwind site of China, where severe smog and BrC were observed during this season. Biomass burning was also an important source; however, unlike in previous studies, where it was identified as a major source during winter, here, it contributed during the whole year. Although many of its properties, sources, and potential impacts remain unknown, this is the first result showing that BrC was prevalent in the PM2.5 fraction in Seoul throughout the year. Also this suggest that BrC and its sources can be long range transported, emphasizing that the optical effect of BrC might be important in East Asia.
AB - The spectral properties of light-absorbing organic aerosol extractions were investigated using 24-h average fine particulate matter (PM2.5) measurements from October 2012 to September 2013 in Seoul, Korea. The light-absorption spectra of water and methanol extracts exhibited strong evidence of brown carbon with Absorption Angstrom Exponent (AAE; fitted between 300 and 700 nm) ranges of 5.84-9.17 and 4.08-5.75, with averages of 7.23 ± 1.58 and 5.05 ± 0.67, respectively. The light absorption of both extracts at 365 nm (Abs365), which is typically used as a proxy for brown carbon (BrC), displayed strong seasonal variations and was well correlated with both water-soluble organic carbon (WSOC; r = 0.81) and organic carbon (OC; r = 0.85), indicating that both primary and secondary organics were sources of BrC in this region. Normalizing the Abs365 of water and methanol extracts to the mass of WSOC and OC yielded average solution mass absorption efficiency (MAE365) of 0.28-1.18 and 0.44-1.45 m2 g-1 C, respectively. MAE365 in Korea were in the same range or slightly lower than those in China, however, despite the same ranges, the seasonal variations were different, suggesting that the sources of light absorbers could be different. Combining the AAE, Abs365, and MAE365 of both extracts and a detailed chemical speciation of filter extracts identified the compounds responsible for the temporal variations of BrC in Korea. During summer, secondary organic aerosol (SOA), photochemically generated from anthropogenic emissions, was the major source; however, during winter, long range transported organics or transported BrC seem to be a source of BrC in Korea, a downwind site of China, where severe smog and BrC were observed during this season. Biomass burning was also an important source; however, unlike in previous studies, where it was identified as a major source during winter, here, it contributed during the whole year. Although many of its properties, sources, and potential impacts remain unknown, this is the first result showing that BrC was prevalent in the PM2.5 fraction in Seoul throughout the year. Also this suggest that BrC and its sources can be long range transported, emphasizing that the optical effect of BrC might be important in East Asia.
KW - AAE
KW - Brown carbon
KW - Light absorption
KW - MAE
KW - Secondary organic aerosol
KW - WSOC
UR - http://www.scopus.com/inward/record.url?scp=84956631933&partnerID=8YFLogxK
U2 - 10.1016/j.atmosenv.2016.01.042
DO - 10.1016/j.atmosenv.2016.01.042
M3 - Article
AN - SCOPUS:84956631933
SN - 1352-2310
VL - 129
SP - 234
EP - 242
JO - Atmospheric Environment
JF - Atmospheric Environment
ER -